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    Sarah Clinton

    Stress-elicited behavioral and physiologic responses vary widely across individuals and depend on a combination of environmental and genetic factors. Adolescence is an important developmental period when neural circuits that guide... more
    Stress-elicited behavioral and physiologic responses vary widely across individuals and depend on a combination of environmental and genetic factors. Adolescence is an important developmental period when neural circuits that guide emotional behavior and stress reactivity are still maturing. A critical question is whether stress exposure elicits contrasting effects when it occurs during adolescence versus adulthood. We previously found that Sprague Dawley rats selectively-bred for low behavioral response to novelty (bred Low Responders; bLRs) are particularly sensitive to chronic unpredictable mild stress (CMS) exposure in adulthood, which exacerbates their typically high levels of spontaneous depressive- and anxiety- like behavior. Given developmental processes known to occur during adolescence, we sought to determine whether the impact of CMS on bLR rats is equivalent when they are exposed to it during adolescence as compared to adulthood. Young bLR rats were either exposed to CMS ...
    The mandatory reporting of firms’ internal control effectiveness continues to be debated by equity market participants, U.S. regulatory agencies and oversight committees. We investigate the implications of material weaknesses in internal... more
    The mandatory reporting of firms’ internal control effectiveness continues to be debated by equity market participants, U.S. regulatory agencies and oversight committees. We investigate the implications of material weaknesses in internal control and SOX 404 required reporting of such for financial analysts because analysts are important intermediaries in the U.S. capital market and it is not known whether analysts’ forecasts or coverage decisions are affected by firms’ internal control problems or reporting, respectively. Results of our empirical tests indicate that analysts provide less accurate forecasts and there is greater forecast dispersion for firms with ineffective internal control. We also find that firms that disclose internal control problems have less analyst coverage and that analyst following declines after the material weakness in internal control is disclosed. The results are robust to controlling for potential self-selection bias and management earnings guidance. Ou...
    The Wistar-Kyoto (WKY) rat is an established depression model characterized by elevated anxiety- and depression-like behavior across a variety of tests. Here we further characterized specific behavioral and functional domains relevant to... more
    The Wistar-Kyoto (WKY) rat is an established depression model characterized by elevated anxiety- and depression-like behavior across a variety of tests. Here we further characterized specific behavioral and functional domains relevant to depression that are altered in WKY rats. Moreover, since early-life experience potently shapes emotional behavior, we also determined whether aspects of WKYs' phenotype were modifiable by early-life factors using neonatal handling or maternal separation. We first compared WKYs' behavior to that of Sprague-Dawley (SD), Wistar, and Spontaneously Hypertensive (SHR) rats in: the open field test, elevated plus maze, novelty-suppressed feeding test, a social interaction test, and the forced swim test (FST). WKYs exhibited high baseline immobility in the FST and were the only strain to show increased immobility on FST Day 2 vs. Day 1 (an indicator of learned helplessness). WKYs also showed greater social avoidance, along with enlarged adrenal gland...
    Schizophrenia is a devastating mental illness affecting millions worldwide with significant financial and emotional burdens for afflicted persons, their families, and society. Considering schizophrenia as a disorder of neuroplasticity... more
    Schizophrenia is a devastating mental illness affecting millions worldwide with significant financial and emotional burdens for afflicted persons, their families, and society. Considering schizophrenia as a disorder of neuroplasticity permits integration of competing neurochemical and neurodevelopmental hypotheses. Recent advances have linked the pathophysiology of schizophrenia with abnormalities of the glutamate neurotransmitter system. Elements of glutamergic neurotransmission implicated in schizophrenia, including glutamate receptors and receptor-associated molecules, have critical roles in long-term potentiation, a molecular correlate of neuroplasticity. We suggest that schizophrenia can be considered a disorder of plasticity, associated with molecular abnormalities of the glutamate synapse.
    ABSTRACT The Securities Offering Reform (SOR), promulgated by the U.S. Securities and Exchange Commission (SEC) in 2005, represents a major change in the seasoned equity offering (SEO) process. SOR eases disclosure restrictions and... more
    ABSTRACT The Securities Offering Reform (SOR), promulgated by the U.S. Securities and Exchange Commission (SEC) in 2005, represents a major change in the seasoned equity offering (SEO) process. SOR eases disclosure restrictions and reduces uncertainty regarding disclosures allowed prior to an SEO. The SEC argued that SOR would result in an improved information environment and benefit capital formation efficiency. In contrast, critics claimed that SOR would allow firms to hype their stock before an SEO to the detriment of the information environment. It is also possible that SOR is not effective in generating greater disclosure and affecting the information environment during equity capital formation because of ongoing concerns such as the litigious climate in the U.S. This paper is the first to examine differences in disclosure and the information environment at the time of seasoned equity capital formation under SOR. Overall, the results suggest that relaxed disclosure restrictions under SOR are associated with greater disclosure immediately preceding the SEO issue date, and greater disclosure is related to a richer information environment with capital formation benefits. During the month before the SEO issue date under SOR, we find more frequent disclosure of management earnings forecasts and Form 8-K filings, and management earnings forecasts are more accurate. In addition, we find disclosure within a week before the SEO issue date under SOR is associated with greater absolute market-adjusted returns (i.e., information magnitude) and more positive stock returns with no reversal afterward (i.e., capital formation benefits through informative disclosure).
    ABSTRACT Using a sample of 1,244 disclosures by 106 proxy contest firms during 1992 - 2001, we document increases in the number of voluntary forward-looking disclosures during proxy contests. Also, disclosure news is more positive during... more
    ABSTRACT Using a sample of 1,244 disclosures by 106 proxy contest firms during 1992 - 2001, we document increases in the number of voluntary forward-looking disclosures during proxy contests. Also, disclosure news is more positive during the proxy contest relative to pre-contest periods. Both of these effects reverse in post-contest periods. Increased disclosure is positively associated with various measures of the likely intensity of the contest. Our results are consistent with strong incentives during proxy contests for managers to use voluntary disclosure to convince shareholders that they are in control of the operating environment and that poor past performance is transitory.
    The neurobiological bases of increased vulnerability to substance abuse remain obscure. We report here that rats that were selectively bred for greater drug-seeking behavior exhibited higher levels of FGF2 gene expression. We then asked... more
    The neurobiological bases of increased vulnerability to substance abuse remain obscure. We report here that rats that were selectively bred for greater drug-seeking behavior exhibited higher levels of FGF2 gene expression. We then asked whether a single FGF2 administration (20 ng/g, s.c.) on postnatal day 2 (PND2) can have a lifelong impact on drug-taking behavior, spatial and appetitive learning and the dopaminergic system. Indeed, early life FGF2 enhanced the acquisition of cocaine self-administration in adulthood. However, early life FGF2 did not alter spatial or operant learning in adulthood. Furthermore, early life FGF2 did not alter gene expression in the dopaminergic system in adulthood. These results suggest that elevated levels of FGF2 may lead to increased drug-taking behavior without altering learning. Thus, FGF2 may be an antecedent of vulnerability for drug-taking behavior and may provide clues to novel therapeutic approaches for the treatment of addiction.
    The present study sought to determine the interaction between the novelty-seeking trait and cocaine treatment on gene expression in the fibroblast growth factor (FGF) system. Specifically, we assessed the regulation of FGFR1 in response... more
    The present study sought to determine the interaction between the novelty-seeking trait and cocaine treatment on gene expression in the fibroblast growth factor (FGF) system. Specifically, we assessed the regulation of FGFR1 in response to cocaine in animals that were selectively bred on the basis of their locomotor response to a novel environment. High-responder (HR) rats are those that exhibit increased locomotor response and exploratory behavior in a novel environment and low-responder (LR) rats are those that exhibit lower levels of exploratory behavior and are less active. Both phenotypes received daily injections of either cocaine (15 mg/kg, i.p.) or saline for 7 consecutive days. Animals were sacrificed 45 min following their last injection and FGFR1 gene expression was assessed in the hippocampus and prefrontal cortex by mRNA in situ hybridization. HR-bred rats exhibited increased FGFR1 mRNA in the hippocampus compared to LR-bred rats. Furthermore, cocaine decreased FGFR1 mRNA in the hippocampus and increased FGFR1 mRNA in the prefrontal cortex. Finally, HR and LR rats differed in their response to cocaine between brain regions. In the hippocampus, cocaine decreased gene expression in HR-bred rats without affecting LR-bred rats, whereas in the prefrontal cortex cocaine increased gene expression in LR-bred rats without affecting HR-bred rats. These results suggest that cocaine interacts with the novelty-seeking trait to alter gene expression. Thus, the FGF system may contribute to individual differences in the response to drugs of abuse.
    Rats selectively bred based on high or low reactivity to a novel environment were characterized for other behavioral and neurobiological traits thought to be relevant to addiction vulnerability. The two lines of animals, which differ in... more
    Rats selectively bred based on high or low reactivity to a novel environment were characterized for other behavioral and neurobiological traits thought to be relevant to addiction vulnerability. The two lines of animals, which differ in their propensity to self-administer drugs, also differ in the value they attribute to cues associated with reward, in impulsive behavior, and in their dopamine system. When a cue was paired with food or cocaine reward bred high-responder rats (bHRs) learned to approach the cue, whereas bred low-responder rats (bLRs) learned to approach the location of food delivery, suggesting that bHRs but not bLRs attributed incentive value to the cue. Moreover, although less impulsive on a measure of 'impulsive choice', bHRs were more impulsive on a measure of 'impulsive action'- ie, they had difficulty withholding an action to receive a reward, indicative of 'behavioral disinhibition'. The dopamine agonist quinpirole caused greater psychomotor activation in bHRs relative to bLRs, suggesting dopamine supersensitivity. Indeed, relative to bLRs, bHRs also had a greater proportion of dopamine D2(high) receptors, the functionally active form of the receptor, in the striatum, in spite of lower D2 mRNA levels and comparable total D2 binding. In addition, fast-scan cyclic voltammetry revealed that bHRs had more spontaneous dopamine 'release events' in the core of the nucleus accumbens than bLRs. Thus, bHRs exhibit parallels to 'externalizing disorders' in humans, representing a genetic animal model of addiction vulnerability associated with a propensity to attribute incentive salience to reward-related cues, behavioral disinhibition, and increased dopaminergic 'tone.'
    Individuals make choices and prioritize goals using complex processes that assign value to rewards and associated stimuli. During Pavlovian learning, previously neutral stimuli that predict rewards can acquire motivational properties,... more
    Individuals make choices and prioritize goals using complex processes that assign value to rewards and associated stimuli. During Pavlovian learning, previously neutral stimuli that predict rewards can acquire motivational properties, becoming attractive and desirable incentive stimuli. However, whether a cue acts solely as a predictor of reward, or also serves as an incentive stimulus, differs between individuals. Thus, individuals vary in the degree to which cues bias choice and potentially promote maladaptive behaviour. Here we use rats that differ in the incentive motivational properties they attribute to food cues to probe the role of the neurotransmitter dopamine in stimulus-reward learning. We show that intact dopamine transmission is not required for all forms of learning in which reward cues become effective predictors. Rather, dopamine acts selectively in a form of stimulus-reward learning in which incentive salience is assigned to reward cues. In individuals with a propensity for this form of learning, reward cues come to powerfully motivate and control behaviour. This work provides insight into the neurobiology of a form of stimulus-reward learning that confers increased susceptibility to disorders of impulse control.
    ABSTRACT The mandatory reporting of firms’ internal control effectiveness continues to be debated by equity market participants, U.S. regulatory agencies and oversight committees. We investigate the implications of material weaknesses in... more
    ABSTRACT The mandatory reporting of firms’ internal control effectiveness continues to be debated by equity market participants, U.S. regulatory agencies and oversight committees. We investigate the implications of material weaknesses in internal control and SOX 404 required reporting of such for financial analysts because analysts are important intermediaries in the U.S. capital market and it is not known whether analysts’ forecasts or coverage decisions are affected by firms’ internal control problems or reporting, respectively. Results of our empirical tests indicate that analysts provide less accurate forecasts and there is greater forecast dispersion for firms with ineffective internal control. We also find that firms that disclose internal control problems have less analyst coverage and that analyst following declines after the material weakness in internal control is disclosed. The results are robust to controlling for potential self-selection bias and management earnings guidance. Our study documents the consequences of ineffective internal control for an important class of financial statement users and suggests the required reporting on the effectiveness of internal control is beneficial to understanding the properties of analysts’ forecasts.
    ABSTRACT Using a unique, hand-gathered sample of 893 forward-looking voluntary disclosures by 70 proxy contest firms during 1992–2001, we examine whether managers temporarily alter the frequency and tone of their disclosures during proxy... more
    ABSTRACT Using a unique, hand-gathered sample of 893 forward-looking voluntary disclosures by 70 proxy contest firms during 1992–2001, we examine whether managers temporarily alter the frequency and tone of their disclosures during proxy contests. Broadly consistent with the corporate control contest hypothesis, we find that, after controlling for performance and other determinants of disclosure, managers increase the frequency of forward-looking voluntary disclosures during the proxy contest relative to the pre-proxy period. After the proxy contest is resolved, managers decrease forward-looking voluntary disclosures. We also find that, after controlling for earnings-based performance and concurrent period stock returns, the voluntary forward-looking disclosure news is more positive, on average, during proxy contests relative to the pre-contest period. In addition, we find limited evidence that disclosure news is more positive during proxy contests relative to the post-contest period, suggesting that the more positive tone of the disclosures during proxy contests is temporary. Our results are robust to alternative estimation methods that model the endogeneity of the proxy contest event and to controlling for management tenure and turnover. In summary, proxy contest voluntary disclosure behavior is consistent with increased incentives to convince shareholders that managers are in control of the operating environment and to signal that poor past performance is transitory. This article is protected by copyright. All rights reserved.
    NMDA receptor dysfunction has been implicated in the pathophysiology of schizophrenia. The NMDA receptor is a multimeric ligand-gated ion channel, and the obligate NR(1) subunit is expressed as one of eight isoforms due to the alternative... more
    NMDA receptor dysfunction has been implicated in the pathophysiology of schizophrenia. The NMDA receptor is a multimeric ligand-gated ion channel, and the obligate NR(1) subunit is expressed as one of eight isoforms due to the alternative splicing of exons 5, 21, and 22. Alternative splicing of NR(1) subunits modulates receptor function by influencing the association of NR(1) with other NMDA receptor subunits and myriad intracellular molecules, such as the postsynaptic density family of proteins that target NMDA receptors to the synaptic membrane and couple it to numerous signal transduction enzymes. Recently, the authors reported that the NMDA receptor subunits NR(1) and NR(2C) are abnormally expressed in the thalamus in schizophrenia. They hypothesized that this reduction is associated with specific NR(1) isoforms and that NMDA receptor-related postsynaptic density proteins are abnormally expressed. Using in situ hybridization, the authors examined expression of the transcripts encoding NR(1) isoforms containing exons 5, 21, or 22, and the NMDA receptor-related postsynaptic density proteins NF-L, PSD93, PSD95, and SAP102. Reduced NR(1) subunit transcript expression was restricted to exon 22-containing isoforms. Increased expression of the NMDA receptor-associated postsynaptic density proteins NF-L, PSD95, and SAP102 was also detected in the thalamus of subjects with schizophrenia. These data support the hypothesis of glutamatergic abnormalities in schizophrenia and suggest that glutamatergic dysfunction may occur not only at the level of receptor expression but also within intracellular pathways associated with glutamate receptor-associated signal transduction.